1. Field of Invention
The present invention relates to a method for controlling adhesive distribution in a flip-chip semiconductor product, and more particularly to a method that increases the efficiency in a chip bonding procedure, and effectively avoids the generation of air bubbles within the adhesive.
2. Related Art
A flip-chip semiconductor product is a chip having metal bumps formed on the bottom and directly mounted on a substrate by ultrasound or heating techniques. Then adhesive is applied to the metal bumps to prevent oxidization of the metal bumps and further enhance the bond between the substrate and the chip, when the adhesive solidifies. Conventionally, the adhesive is applied along the flange of the chip to flow by capillary action into the space between the substrate and the bottom of the chip.
However, the conventional method of applying the adhesive on the metal bumps has some defects that need to be overcome and are hereinafter listed.
1. Because of the varied specifications of chips, the arrangement of metal bumps on chips with different specifications accordingly are positioned differently. Therefore the adhesive distribution is greatly affected by the different arrangements of the metal bumps. With reference to FIG. 6, multiple metal bumps (51) are disposed on the bottom of a chip (50), and adhesive (60) is provided along an edge of the chip (50) and flows to the metal bumps (51). Since the bumps (51) are disposed non-uniformly, for example, the arrangement density in region xe2x80x9caxe2x80x9d is higher than that in region xe2x80x9cbxe2x80x9d, the adhesive (60) that flows to region xe2x80x9caxe2x80x9d flows faster than the adhesive (60) that flows to region xe2x80x9cbxe2x80x9d. When an empty region exists on the chip (50), such as the region indicated by xe2x80x9ccxe2x80x9d, the adhesive (60) flowing to metal bumps (51) formed around the empty region xe2x80x9cdxe2x80x9d is very difficult to control.
2. Since the adhesive is difficult to control, the adhesive usually cannot be completely applied in a single application but needs to be applied repeatedly. Therefore the efficiency of such a process is very low.
3. Because the speed that the adhesive flows is not easy to control and the adhesive needs to be repeatedly applied to the metal bumps, the opportunity for air bubbles to form in the adhesive is extremely high. When the flip-chip semiconductor product is heated in subsequent processes, the air bubbles formed in the adhesive will expand and explode damage or break the structure of the flip-chip semiconductor product.
To overcome the shortcomings, the present invention provides a method to control the speed that the adhesive applied to a flip-chip semiconductor product flows to mitigate and obviate the aforementioned problems.
An objective of the invention is to provide a method of controlling the adhesive distribution on a flip-chip semiconductor product thereby causing the adhesive to be distributed uniformly and to prevent the generation of air bubbles in the adhesive.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.